问题 问答题

现有某图书销售数据库,其关系表结构如下: 图书表(图书编号,图书名称,出版社编号,出版社名称,出版时间,出版数量,版次) 图书销售表(图书编号,销售日期,销售数量,书店编号,读者编号,读者姓名,读者电话) 书店表(书店编号,联系电话,所在城市编号,城市名称) Ⅰ.系统所涉及的数据存在如下约束: 出版社可以出版多本图书,一本图书只能在一个出版社出版,在该系统记录的图书出版信息包括出版时间、版次及出版数量。 Ⅱ.一个书店可以出售多本图书给多个读者,每位读者可以从多个书店购买多本图书,一本图书可以通过多个书店出售给读者,书店把图书出售给读者后会在系统中记录售书日期和售书数量。 Ⅲ.每个书店只能位于一个城市,一个城市可以有多个书店。 ①以图书销售表为例说明原数据库设计的不合理之处。 ②给出该数据库符合3NF要求的全部关系模式,并指出关系模式中的全部主码和外码。

答案

参考答案:

解析:①图书销售表中,读者信息应该单独新建一张表,否则就会造成大量的数据冗余。 ②出版社表(出版社编号,出版社名称)主码:出版社编号 出版表(出版社编号,图书编号,出版时间,出版数量,版次)主码:(出版社编号,图书编号) 图书表(图书编号,图书名称)主码:图书编号 书店表(书店编号,联系电话,所在城市编号)主码:书店编号 城市表(所在城市编号,城市名称)主码:所在城市编号 读者表(读者编号,读者姓名,读者电话)主码:读者编号 图书销售表(图书编号,读者编号.销售日期,销售数量,书店编号)主码:(图书编号,读者编号) 本题考查的主要是数据库设计优化、关系数据模型转换及规范化处理。

单项选择题
填空题

The Economist recognises these talented people through its annual Innovation Awards, presented in six fields: bioscience, computing and communications, energy and environment, business-process innovation, consumer products and a flexible "no boundaries" category. The awards were presented at a ceremony in London on November 9th by John Micklethwait, The Economist’s editor-in-chief.
And the winners were:
Bioscience:
Marvin Caruthers, professor of chemistry and biochemistry at the University of Colorado at Boulder, for the development of automated DNA synthesis--the ability to "print out" arbitrary strands of genetic material.
(41) Computing and communications:
a creative individual who dreams up new ideas of computing and communi6ations and turn them into reality.
(42) Energy and environment:
a creative individual who dreams up new ideas of energy and environment and turn them into reality.
(43) No boundaries:
a creative individual who dream up new ideas of internet and turn them into reality.
(44) Business-process innovation:
a creative individual who dreams up new ideas of business-process and turn them into reality.
(45) Consumer products:
a creative individual who dreams up new ideas of consumer products and turn them into reality.
We extend our congratulations to the winners, and our thanks to the judges.
[A] Nicolas Hayek, chairman of Swatch, for revitalising the Swiss watch industry. During the 1980s Switzerland’s legendary watch industry fell into decline, with exports falling by half within a decade as a result of Japanese competition. Mr. Hayek’s response was to consolidate the industry to create the Swatch Group. It went on to beat the Japanese at their own game, creating the bestselling watch brand in history and becoming the largest watchmaker in the world, with a quarter of the market.
[B] Janus Friis and Niklas Zennstrom of Skype, for the development of internet file-sharing and telephony using peer-to-peer technology, which allows millions of computers to link up over the internet without central co-ordination. In 2000 Messrs Friis and Zennstrom launched KaZaA, which became the dominant means of sharing music and video files, despite attempts by the entertainment industry to shut it down. Skype, launched in 2003, lets users make free phone calls over the internet, forcing traditional telecoms operators to slash their prices.
[C] Sam Pitroda, chief executive of WorldTel, for pioneering India’s communications revolution. In 1987 Mr. Pitroda was asked by Rajiv Gandhi, the Indian prime minister, to help democratise access to telecommunications. His response was to deploy instantly recognizable yellow telephone kiosks in every town and village. This helped to release India’s telecoms industry from state control and opened it up to private firms, paving the way for a technology boom. He now promotes similar policies in other countries.
[D] Pierre Omidyar, founder and chairman of eBay, for the development of electronic marketplace technology and his promotion of access to markets as a tool for social change. Mr. Omidyar set up eBay in 1995 with the aim of creating a marketplace accessible to any internet user. The business was profitable by 1996. People all over the world buy and sell items in 45 000 categories; some even make a living trading on eBay.
[E] Hernando de Soto, founder and president of the Institute for Liberty and Democracy. Mr. de Soto argues that bureaucracy and the lack of formal property rights are major causes of poverty in developing countries. Red tape and the lack of legal title to property, preventing its use as collateral, make it hard for the poor to establish or expand businesses. While serving as economic adviser to the Peruvian government, Mr. de Soto initiated a property-titling scheme which helped 1.2m families. Similar reforms have been implemented in El Salvador, Haiti, Tanzania and Egypt. Mr. de Soto has also championed the use of league tables to shame governments into cutting red tape.
[F] Johannes Poulsen, former chief executive, Vestas Wind Systems, for the commercialisation of wind energy. In 1987 Mr. Poulsen took the helm at Vestas, then a small Danish firm with 60 employees. By the time he retired in 2002, Vestas had 5 000 employees and a quarter of the world market for wind turbines. Under Mr. Poulsen, Vestas greatly improved the efficiency of wind turbines, reducing costs and making wind power more competitive.